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Reduce an STL for Fusion 360

Fusion 360 imports any STL, but Convert Mesh to a solid body warns above 10,000 triangles and Autodesk's own guidance is to keep it around that figure. A typical downloaded STL has 100 to 1,000 times more. This page opens the reducer at 5 MB, about 100,000 triangles, a workable size for editing; set 1 MB for a convertible one.

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Drop an STL file here or click to browse
Up to 300 MB · .stl only
Choose STL file
1
Upload STL
2
Set target MB
3
Download
MB
1 MB500 MB

We aim for exactly this size. Quality-preserving quadric decimation stops as soon as the file fits. If the mesh cannot be reduced further without breaking, we return the smallest safe result.

Pick an STL file to continue.
🔒 Files are processed on our server in isolated memory and removed within 15 minutes of your download.

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The limit: Fusion 360

File size cap
no fixed cap
Triangle cap
10,000
This page opens the reducer at
5 MB

This page opens the reducer at 5 MB. Source: Autodesk support, Convert Mesh performance (checked 2026-09).

Why the file is over it

Meshes people bring into Fusion are scans and Thingiverse downloads made for printing, where triangle count is free. Fusion's mesh-to-BRep conversion creates a face per triangle, so 500,000 triangles become 500,000 faces and the timeline stalls. Fusion's own Reduce command works on the imported mesh but is slow on large inputs and has no size target.

How to get under it

  1. 1Drop the STL below. The target is preset to 5 MB; use 1 MB if you intend to Convert Mesh to a solid.
  2. 2Press Reduce. The tool keeps edges and flat faces, which is what you need for a part you plan to modify.
  3. 3Import the reduced STL into Fusion (Insert Mesh) and run Convert Mesh or Modify → Reduce for the final step.
Reduce for Fusion 360 (target 5 MB)

What to expect

A 48 MB scan (one million triangles) to 1 MB keeps about 21,000 triangles: mechanical shapes survive, organic surfaces become visibly faceted, which is fine as a reference body and required for a fast conversion. At 5 MB (105,000 triangles) the shape is still smooth and Fusion stays responsive for sectioning and measuring.

Other ways

Fusion's Modify → Reduce works on meshes under a few hundred thousand triangles but can take minutes and has no byte target. For a CAD part, re-exporting from its source with a coarser tolerance beats any decimation.

Questions

Why does Convert Mesh take forever?

It makes a BRep face per triangle. 10,000 faces is the practical ceiling for a usable timeline; reduce to under 1 MB first.

Will a reduced mesh still measure correctly?

Yes for anything larger than the collapse tolerance. Hole diameters and overall dimensions are unchanged; only micro texture is gone.

Can I reduce a mesh Fusion exported?

Yes. Fusion's STL export at High refinement can be tens of MB; reduce it with the target your destination needs.